|Abstracts on Global Climate Change|
Namaqualand - A brief overview of the physical and floristic environment
JOURNAL OF ARID ENVIRONMENTS 70:4 570-587
This paper provides a brief introduction to the physical environment of Namaqualand as well as an overview of patterns of plant diversity. The diverse array of parent material and geological processes that have shaped the region since the break up of Gondwanaland have created a complex, and sometimes dynamic physical environment, that is partly responsible for the patterns and processes observed in the biota today. The contemporary climate is characterised by relatively reliable, albeit low (50-250 mm pa), winter rainfall (> 60% winter precipitation) arriving between May and September. East of the central mountains, tropical thunderstorms penetrate the region in late summer (February April). The presence of the cold Atlantic Ocean in the west not only moderates temperatures throughout Namaqualand (mean max summer temperature < 30 degrees C), but also provides alternative sources of moisture in the form of coastal fog and heavy dew experienced in winter months. Recent analyses show that the flora of the Succulent Karoo is part of the Cape Floral Kingdom, now termed the Greater Cape Floral Kingdom. It is one of only two desert regions recognised as a global biodiversity hot-spot and contains an estimated 6356 plant species in 168 families and 1002 genera. Namaqualand, which comprises about one quarter of the area of the Succulent Karoo, contains about 3500 species in 135 families and 724 genera, with about 25% of this flora endemic to Namaqualand. This remarkable diversity, however, is not distributed evenly throughout the region, but is concentrated in many local centres of endemism usually associated either with quartzite mountain complexes or lag-gravel plains (quartz-patches). A major exception to the general pattern of centres of diversity is the true Fynbos vegetation of the highest Kamiesberg peaks where rainfall exceeds 400 mm pa. Suggested determinants of the region’s exceptional floral diversity include the complex physical environment, a unique past and present climate and the region’s diverse fauna, most notably insects. The challenge for the current inhabitants and scientists working in the region is to develop a better understanding of this ecosystem so that they will be equipped to deal with the challenges posed by the demands for land and the prospect of global climate change. (c) 2007 Elsevier Ltd. All rights reserved.
Sifting the future from the past: a personal assessment of trends impacting the Australian rangelands
RANGELAND JOURNAL 29:1 3-11
The fore-sighting exercise undertaken at the Australian Rangeland Society Conference at Port Augusta 10 years ago in 1996 developed four scenarios: ‘economic growth’, ‘best practice’, ‘extra green’ and ‘partial retreat’. These were later collapsed into two broad directions, ` looking out’ (the economic rewards generated by a full application of free market policies with rangeland enterprises having strong external linkages will result in production and management efficiencies which benefit the Australian economy) and ‘looking in’ (rangeland Australia and its human, economic and ecological resources will be best served by the development and maintenance of strong local communities in each rangeland region). It was anticipated that ` looking out’ would apply to only a few rangeland regions where pastoral production is highly valued and rangelands are resilient; ` looking in’ would apply to the majority of the rangelands where other values might outweigh pastoral production in the future and where the rangeland resource is considered less resilient. Given the world’s embrace of economic and trade globalisation, and the dominance in the federal sphere of one coalition government and one prime minister, it seems inevitable that across Australia the last 10 years were dominated by the ` looking out’ direction, while many marginal rangelands had few options but to ‘look in’. The 1996 discussions failed to appreciate fully the importance in shaping today’s world of singular issues such as terrorism, global climate change, potential disease pandemics, the emergence of China and India and, in an Australian rangelands context, the continuing success of the northern beef industry. In the interim, rangelands science has produced an impressive underpinning of integrative information led both by industry investment and government funding. However, long-term resilience is still not assured in many areas of Australia’s rangelands. It continues to be outpaced by those four horsemen of the ( rangelands) apocalypse: the need for growth, periodic droughts, personal gain and introduced organisms. During the next 2 decades the rangelands will be buffeted by many of the same old issues and well as obvious emerging ones. Important human-centric ones will be the tension between European and Aboriginal demographic trends, the increased economic dominance of mining, tourism and defence in the rangelands, and the ‘sponge effect’ of successful towns and particular enterprises. Ecological and bio-physical issues will include carbon trading, energy generation, water catchments, weeds and diseases and agricultural incursions into the northern rangelands. The broad directions of ‘looking out’ and ‘looking in’ still retain some currency for today’s rangeland decision makers but are now embedded in far stronger and shifting currents that are frequently determined by global and national dynamics, rather than local issues. A distinguishing feature of the Australian rangelands is that they are still essentially intact (apart from their fauna) in a world context and may gain future ecological and economic advantage by remaining so. How to retain this status remains one of the great challenges for the next generation of Australian rangelanders.
Experimental studies on homogeneous charge CI engine fueled with LPG using DEE as an ignition enhancer
Jothi, NKM Nagarajan, G Renganarayanan, S
RENEWABLE ENERGY 32:9 1581-1593
Producing and using renewable fuels for transportation is one approach for sustainable energy future for the world. A renewable fuel contributes lesser global climate change. The present work reports on the utilization of liquified petroleum gas (LPG) as a primary fuel with diethyl ether (DEE) as an ignition enhancer in a direct injection diesel engine. LPG has a simpler hydrocarbon structure than conventional fuels. DEE is recently reported as a renewable fuel and to be a low-emission high-quality diesel fuel replacement. A single cylinder, four-stroke, water-cooled naturally aspirated DI diesel engine having rated output of 3.7 kW at 1500 rpm was used for the experiments. Measurements were made to study the performance, combustion and emissions characteristics. From the results, it is observed that, the brake thermal efficiency lower by about 23% at full load with a reduction of about 65% NO emission than the diesel operation. The maximum reduction in smoke and particulate emissions is observed to be about 85% and 89%, respectively, when compared to that of diesel operation, however an increase in CO and HC emissions was observed. (c) 2006 Elsevier Ltd. All rights reserved.
Modelling energy systems for developing countries
Urban, F Benders, RMJ Moll, HC
ENERGY POLICY 35:6 3473-3482
Developing countries’ energy use is rapidly increasing, which affects global climate change and global and regional energy settings. Energy models are helpful for exploring the future of developing and industrialised countries. However, energy systems of developing countries differ from those of industrialised countries, which has consequences for energy modelling. New requirements need to be met by present-day energy models to adequately explore the future of developing countries’ energy systems. This paper aims to assess if the main characteristics of developing countries are adequately incorporated in present-day energy models. We first discuss these main characteristics, focusing particularly on developing Asia, and then present a model comparison of 12 selected energy models to test their suitability for developing countries. We conclude that many models are biased towards industrialised countries, neglecting main characteristics of developing countries, e.g. the informal economy, supply shortages, poor performance of the power sector, structural economic change, electrification, traditional bio-fuels, urban-rural divide. To more adequately address the energy systems of developing countries, energy models have to be adjusted and new models have to be built. We therefore indicate how to improve energy models for increasing their suitability for developing countries and give advice on modelling techniques and data requirements. (c) 2007 Elsevier Ltd. All rights reserved.
Diversity and zonal distribution of arbuscular mycorrhizal fungi on the northern slopes of the Tianshan Mountains
Shi, ZY Chen, ZC Zhang, LY Feng, G Christie, P Tian, CY Li, XL
SCIENCE IN CHINA SERIES D-EARTH SCIENCES 50: Suppl. 1 135-141
The arbuscular mycorrhizal (AM) fungal status of the 20 most common plant species distributed in 4 vegetation types (meadow steppe, desert steppe, steppe desert and typical desert) on the northern slopes of the Tianshan Mountains was investigated. Samples of the plant species and their rhizosphere soils were collected from the 4 vegetation zones and examined to compare their mycorrhizal status, AM fungal spore densities, biovolumes, and community structures. 28 AM fungal species were isolated from the rhizosphere soils: of these, 5 belonged to Acaulospora, 1 to Archaeospora and 22 to Glomus. 5 AM fungi, Glomus aggregatum, G. claroideum, G. deserticola, G. etunicatum and G. sinuosum, were observed in all 4 zonal types. No significant differences were observed in mean proportion of root length colonized by AM fungi among the plant species within each zonal type. Comparing the 4 zonal types, Plantago minuta (84.5%) in steppe desert and Eremopyrum orientale (83.1%) in typical desert showed the highest root colonizatsion rates. AM fungal spore densities and biovolumes were significantly different in the different zonal types. AM fungal spore densities and biovolumes, species richness and diversity were highest in meadow steppe and lowest in typical desert.
Evaluating long-term trends in annual and seasonal precipitation in Taiwan
Yu, PS Yang, TC Kuo, CC
WATER RESOURCES MANAGEMENT 20:6 1007-1023
This work studies long-term rainfall variations in Taiwan and provides local climate change analyses to global climate change. Around a century of rainfall data from 33 rain-gauges populate the database used herein. Statistical tests, such as cumulative deviations, Mann-Whitney-Pettitt statistics and the Kruskal-Wallis test, were first employed to determine whether annual rainfall series exhibit any regular trend. Analytical results indicate that the annual rainfall has increased in northern Taiwan, declined in central and southern Taiwan, and exhibited no clear tendency in Eastern Taiwan. Almost all of these rainfall series changed significantly around 1960, which date divides historical rainfall series into two sample groups. This change in the seasonal rainfall was further investigated.
Frequency of debris flows and rockfall along the Mendoza river valley (Central Andes), Argentina: Associated risk and future scenario
QUATERNARY INTERNATIONAL 158: 110-121
The frequency of debris flows and rockfalls was estimated by temporal distribution of these events during the last 50 years. This parameter was expressed by annual probability of occurrence and mean interval of recurrence of historical events. More recurrent events in this sector of the Central Andes are associated with the Guido locality and tunnels situated along International road No. 7. Furthermore, these events are more frequent in Cordillera Frontal where the mean recurrence interval was lower than in Precordillera. The maximum interval of recurrence is rarely greater than 20 years, showing the activity of these events on human lives and infrastructure in this region. The accuracy of the determined recurrence frequency is discussed. A future scenario indicates that landslides will be probably more frequent under global climate change. As a consequence, those most vulnerable elements in the region, the international access routes, may be severely damaged in the future, implying an adverse impact in our regional economy. (c) 2006 Elsevier Ltd and INQUA. All rights reserved.
Personal values, beliefs, and ecological risk perception
Slimak, MW Dietz, T
RISK ANALYSIS 26:6 1689-1705
A mail survey on ecological risk perception was administered in the summer of 2002 to a randomized sample of the lay public and to selected risk professionals at the U.S. Environmental Protection Agency (US EPA). The ranking of 24 ecological risk items, from global climate change to commercial fishing, reveals that the lay public is more concerned about low-probability, high-consequence risks whereas the risk professionals are more concerned about risks that pose long-term, ecosystem-level impacts. To test the explanatory power of the value-belief-norm (VBN) theory for risk perception, respondents were questioned about their personal values, spiritual beliefs, and worldviews. The most consistent predictors of the risk rankings are belief in the new ecological paradigm (NEP) and Schwartz’s altruism. The NEP and Schwartz’s altruism explain from 19% to 46% of the variance in the risk rankings. Religious beliefs account for less than 6% of the variance and do not show a consistent pattern in predicting risk perception although religious fundamentalists are generally less concerned about the risk items. While not exerting as strong an impact, social-structural variables do have some influence on risk perception. Ethnicities show no effect on the risk scales but the more educated and financially well-off are less concerned about the risk items. Political leanings have no direct influence on risk rankings, but indirectly affect rankings through the NEP. These results reveal that the VBN theory is a plausible explanation for the differences measured in the respondents’ perception of ecological risk.
Water in the Earth’s atmosphere
Quante, M Matthias, V
JOURNAL DE PHYSIQUE IV 139: 37-61
Water is the key to our existence on this planet and it is involved in nearly all biological, geological, and chemical processes. Life on Earth depends very much on the remarkable properties of water. The availability of freshwater is for many regions one of the key concerns in connection with global climate change. The atmosphere contains only about 0.001% of the water available on our planet. Despite this small amount its horizontal and vertical distribution plays a key role in the global water cycle and the Earth’s climate. The atmosphere has direct connections to most of the other reservoirs and steers the redistribution of water between them with an average turnover time of about 10 days. Evaporation over the oceans exceeds precipitation and over land evapotranspiration amounts only to 2/3 of the precipitation reaching the ground. Consequently, there is a net flux of water from the oceans towards the continents, of course via the atmosphere, which has the largest overall volume of fluxes. Water is present in the atmosphere as solid, liquid, or gas. Water vapour is the most important greenhouse gas in the atmosphere and, in addition, changes of water phase and cloud-radiation interaction contribute strongly to the global energy cycle. Water is also a physically and chemically integral part of other biogeochemical cycles. Although there have been large efforts and improvements in recent years, uncertainties in quantifying the components of the atmospheric water cycle still exist. Observational capabilities on the global scale are not satisfactory at present, but the advent of new satellites devoted to the global observation of precipitation and cloud systems along with dedicated modelling projects certainly will improve the situation. Progress is urgently needed to adequately contribute to the answer of one of the central questions in the context of global warming: Is the hydrological cycle accelerating?.
Low clouds and cloud immersion enhance photosynthesis in understory species of a southern Appalachian spruce-fir forest (USA)
Johnson, DM Smith, WK
AMERICAN JOURNAL OF BOTANY 93:11 1625-1632
High-attitude forests of the southern Appalachian Mountains (USA) are frequently immersed in clouds, as are many mountain forests. They may be particularly sensitive to predicted increases in cloud base altitude with global warming. However, few studies have addressed the impacts of immersion on incident sunlight and photosynthesis. Understory sunlight (photosynthetically active radiation, PAR) was measured during clear, low cloud, and cloud-immersed conditions at Mount Mitchell and Roan Mountain, NC (USA) along with accompanying photosynthesis in four representative understory species. Understory PAR was substantially less variable on immersed vs. clear days. Photosynthesis became light-saturated between similar to 100 and 400 mu mol center dot m(-2). s(-1) PAR for all species measured, corresponding closely to the sunlight environment measured during immersion. Estimated daily carbon gain was 26% greater on clear days at a more open canopy site but was 22% greater on immersed/cloudy days at a more closed canopy site. F-v/F-m (maximum photosystem II efficiency) in Abies fraseri seedlings exposed to 2.5 min full sunlight was significantly reduced (10%), indicating potential reductions in photosynthesis on clear days. In addition, photosynthesis in microsites with canopy cover was nearly 3-fold greater under immersed (2.6 mmol center dot m(-2) center dot h(-1)) vs. clear conditions (0.9 mmol center dot m(-2) center dot h(-1)). Thus, cloud immersion provided more constant PAR regimes that enhanced photosynthesis, especially in shaded microsites. Future studies are needed to predict the survival of these refugial forests under potential changes in cloud regimes.
Farmers’ annual activities are not tracking the speed of climate change
Menzel, A Von Vopelius, J Estrella, N Schleip, C Dose, V
CLIMATE RESEARCH 32:3 201-207
Global climate change impacts are already tracked in many physical and biological systems and they reveal a consistent picture of changes, e.g. an earlier onset of spring events in mid and higher latitudes and a lengthening of the plant growing season. However, available results are mainly based on the study of wild plants, whereas only a few studies have hinted at an earlier spring onset for agricultural plants. So far, no comprehensive study has compared phenological shifts between agricultural crops, fruit trees and wild plants. We analysed phenological time series of 93 phases in Germany (1951-2004) employing Bayesian nonparametric function estimation, and found that events related to the production of annual crops clearly differ from spring and summer events in wild plants and fruit trees. While non-farmer driven agricultural events and spring and summer growth stages of wild plants and fruit trees advanced (i.e. occurred earlier) by 4.4 to 7.1 d decade(-1), farming indicators, such as sowing and subsequent emergence of spring and winter crops, as well as harvesting, advanced by only 2.1 d decade(-1). The estimated functional behaviour and emergence of discontinuous changes are clearly different between the 2 groups. We conclude that phenological responses to temperature changes are only reflected in data of wild plants, fruit trees and those spring growth stages of winter crops and later growth stages of spring crops which are exclusively triggered by climate, while other changes due to agricultural production are subject to management practice alterations.
Determination of forest growth trends in Komi Republic (northwestern Russia): combination of tree-ring analysis and remote sensing data
Lopatin, E Kolstrom, T Spiecker, H
BOREAL ENVIRONMENT RESEARCH 11:5 341-353
It is very important to detect changes in forest productivity due to the global change on a large scale. In this work, the evolution of the vegetation in the Komi Republic (northwestern Russia) from 1982 to 2001 was analyzed using NOAA AVHRR PAL time series. A statistically significant correlation (adjusted r(2) = 0.44-0.59) between Normalized Difference Vegetation Index (NDVI) data and tree ring width (261 living trees) was identified for the territory of the Komi Republic. The increased site productivity reflected an increase of integrated NDVI values from June to August. This allows NDVI to be used as a proxy for estimation of forest growth trends for the recent decades. A positive and significant trend in NDVI data was identified from 1982 to 2001, coinciding with an increase in site productivity in the study area. The decrease in precipitations coincided with an increase in site productivity (highest r(2) was 0.71). The increase in productivity reflected in NDVI data is maximal on the sites with increased temperature and decreased precipitations. In the Komi Republic the distribution of the trends in NDVI data changes on the south-west to north-east gradient. NDVI data could be used to increase spatial resolution of tree ring width series. Taking into account the relatively small role of human activity in the Komi Republic compared with Europe, the site productivity during recent decades also increased in relatively untouched forests.
Predicted climate change alters the indirect effect of predators on an ecosystem process
Lensing, JR Wise, DH
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 103:42 15502-15505
Changes in rainfall predicted to occur with global climate change will likely alter rates of leaf-litter decomposition through direct effects on primary decomposers. In a field experiment replicated at two sites, we show that altered rainfall may also change how cascading trophic interactions initiated by arthropod predators in the leaf litter indirectly influence litter decomposition. On the drier site there was no interaction between rainfall and the indirect effect of predators on decomposition. In contrast, on the moister site spiders accelerated the disappearance rate of deciduous leaf litter under low rainfall, but had no, or possibly a negative, indirect effect under high rainfall. Thus, changes resulting from the more intense hydrological cycle expected to occur with climate change will likely influence how predators indirectly affect an essential ecosystem process.
Relationship between climate, pollen concentrations of Ambrosia and medical consultations for allergic rhinitis in Montreal, 1994-2002
Breton, MC Garneau, M Fortier, I Guay, F Louis, J
SCIENCE OF THE TOTAL ENVIRONMENT 370:1 39-50
The aim of this study is to evaluate the influence of meteorological factors on Ambrosia pollen concentrations and its impact on medical consultations for allergic rhinitis of residents from various socio-economic levels in Montreal (Quebec, Canada) between 1994 and 2002. The study was conducted to recognize the sensitivity of pollen productivity to daily climate variability in order to estimate the consequences on human health vulnerability in the context of global climate change. Information related to medical consultations for allergic rhinitis due to pollen comes from the Quebec Health Insurance Board (Regie de l’assurance-maladie du Quebec). Ambrosia pollen concentration was measured by the Aerobiology Research Laboratories (Nepean, Ontario). Daily temperature (maximum, minimum, and mean) and precipitation data were obtained from the Meteorological Service of Canada. Socio-economic data come from the 1996 and 2001 census data of Statistics Canada. Between 1994 and 2002, during the Ambrosia pollen season, 7667 consultations for allergic rhinitis due to pollen were recorded. We found a significant association between the number of medical consultations and pollen levels. Significant associations were detected for over-consultation the day of exposure, 1, 2, 3 and 5 days after exposure to high levels of pollen. The consultation rate is higher from low-income residents (3.10 consultations per 10,000 inhabitants) than for high-income (1.65 consultations per 10,000 inhabitants). Considering the demonstrated impact of pollen levels on health, it has become critical to ensure adequate monitoring of Ambrosia and its meteorological sensivity in the context of the anticipated climate change and its potential consequences on human health. (c) 2006 Elsevier B.V. All rights reserved.
Ecological niche modelling and prioritizing areas for species reintroductions
Martinez-Meyer, E Peterson, AT Servin, JI Kiff, LF
ORYX 40:4 411-418
Species reintroduction programmes, in prioritizing areas for reintroductions, have traditionally used tools that include measures of habitat suitability and evaluations of area requirements for viable populations. Here we add two tools to this approach: evaluation of ecological requirements of species and evaluation of future suitability for species facing changing climates. We demonstrate this approach with two species for which reintroduction programmes are in the planning stages in Mexico: California condor Gymnogyps californianns and Mexican wolf Canis lupus baileyi. For the condor, we identify three areas clustered in the Sierra San Pedro Martir, Baja California; for the wolf, we identify a string of suitable sites along the Sierra Madre Occidental of western Mexico. We discuss the limitations of this approach, identifying ways in which the models illustrated could be made more realistic and directly useful to reintroduction programmes.
Lichen flora around the Korean Antarctic Scientific Station, King George Island, Antarctic
Kim, JH Ahn, IY Hong, SG Andreev, M Lim, KM Oh, MJ Koh, YJ Hur, JS
JOURNAL OF MICROBIOLOGY 44:5 480-491
As part of the long-term monitoring projects on Antarctic terrestrial vegetation in relation to global climate change, a lichen floristical survey was conducted around the Korean Antarctic Station (King Sejong Station), which is located on Barton Peninsula, King George Island, in January and February of 2006. Two hundred and twenty-five lichen specimens were collected and sixty-two lichen species in 38 genera were identified by morphological characteristics, chemical constituents, TLC analysis and ITS nucleotide sequence analysis.
Aquatic plants diversity in arid zones of Northwest China: patterns, threats and conservation
Li, ZQ Yu, D Xiong, W Wang, D
BIODIVERSITY AND CONSERVATION 15:11 3417-3444
We investigated aquatic plant diversity by conducting the field investigation and collecting the published data in the arid regions of Northwest China. Two hundred and twenty four taxa of vascular aquatic plants representing 64 genera and 34 families occur in this area, 8.48% of which are endemic. Among these, 1 genus and 6 species were new state records and 1 family, 9 genera and 29 species were new area records. Typhaceae, Potamogetonaceae, Juncaginaceae and Haloragaceae were the most frequent families (considering relative frequency of occurrence), whereas Cyperaceae, Potamogetonaceae and Ranuncnlaceae are the most species-rich. The most frequent genera were Typha, Potamogeton, and Triglochin, and the most species-rich were Potamogeton, Eleocharis and Scirpus. The most frequent species are Triglochin palustre, Myriophyllum spicatum, Potamogeton pectinatus and Typha angustifolia. Aquatic plants diversity is distributed unevenly in the region. The maximum species occurs in Dzungarian basin while the least species in Hexi corridor. The aquatic flora in arid zone of China is not distinctive although some endemic species are found, most species are widely distributed. Local aquatic plants diversity can be influenced by many factors such as hydrological alteration, habitat loss, over-grazing, high human population pressure, global climate change, an inappropriate economic development policy. Among them, the largest threat to aquatic plants biodiversity may be habitat loss due to hydrological alteration. In order to conserve the aquatic plants biological resources and biodiversity in this region, some strategies and measures must be suggested including strengthening scientific research and biodiversity education in the local people, balancing economic development and ecological conservation, and enhancing governmental assistance and subsidy to the local residents.
Soil carbon turnover in the McMurdo Dry Valleys, Antarctica
Barrett, JE Virginia, RA Parsons, AN Wall, DH
SOIL BIOLOGY & BIOCHEMISTRY 38:10 3065-3082
Terrestrial ecosystems of the Antarctic Dry Valleys are among the most inhospitable soil environments on Earth due to climate and substrate limitations over biota. These ecosystems present a challenge to understanding controls over carbon (C) cycling because likely sources of organic matter are 10(2)-10(4) yrs old and in situ soil respiration is typically less than 1.0 mu mol CO2 m(-2) s(-1). In this paper we describe an analytical approach to characterize kinetic pools of labile and recalcitrant soil C, and estimate C turnover in dry valley soils based upon these descriptions. Rate parameters for C turnover were derived from laboratory incubations conducted under a range of soil moistures and temperatures. We developed a C flux and reservoir model using these rate parameters along with published estimates of internal C transformations in soil microbial ecosystems, and a previously described primary production (NPP) model for Antarctic endolithic communities. We found that decomposition in 120 d incubations was well described by double-exponential rate kinetics, and that temperature, moisture and substrate availability significantly influenced observed rates of soil respiration. Simulations of soil C cycling based upon these parameters produced initially high rates of soil respiration following inputs of external organic matter, with mean residence times for C of 10-60 yrs. Soil organic C content equilibrated at 44-140% of observed levels within 1000 yrs. Simulations of equilibrium C were sensitive to NPP, microbial efficiency (Y), and the distribution of C inputs into labile and passive pools, indicating that more thorough investigation of microbial influence over the C cycle in dry valley soils is necessary. (c) 2006 Elsevier Ltd. All rights reserved.
The northern geographic range limit of the intertidal limpet Collisella scabra: a test of performance, recruitment, and temperature hypotheses
ECOGRAPHY 29:5 709-720
A decline in abundance towards a species’ range boundary is often interpreted as evidence of a decline in individual success, and is usually assumed to reflect a decline in suitable environmental conditions. Gradual declines towards high latitude range boundaries are frequently attributed to limitations on organismal tolerance of cold temperature. Rarely have these two assumptions been empirically tested. The intertidal gastropod Collisella scabra declines monotonically in abundance from 435 to < 1 m(-2) over the northern 300 km of its geographic distribution. I examined temperature, adult performance (survival, growth, reproduction), and recruitment at five locations in this region of decline. Mortality ranged from 4.9 to 11.2% per month, but was highest at the lowest latitude study site. Growth rates ranged from 0 to 5.2 mm yr(-1), but were generally lower at lower latitude sites. Gonad development was high in the three populations examined, but the possibility of infrequent spawning at high latitude sites could not be excluded. Finally, a comparison of performance differences among populations with temperature revealed clear effects of temperature on both growth and mortality; however, the patterns were not consistent with a hypothesis of cold stress at the range boundary. Overall there was little evidence for either reduced performance or increasing cold stress in low density high latitude populations. Over the same 300 km, recruitment declined monotonically from a mean of six recruits per 625 cm(2) to less than one; suggesting that limitations on recruitment, rather that adult performance, are responsible for low abundance in marginal populations. Several hypotheses for the decline in recruitment are discussed in the paper and the most likely explanation appears to be an increase in the distance between populations at the range margin, reducing the chances that dispersing larvae find suitable habitat for settlement.
European phenological response to climate change matches the warming pattern
Menzel, A Sparks, TH Estrella, N Koch, E Aasa, A Ahas, R Alm-Kubler, K Bissolli, P Braslavska, O Briede, A Chmielewski, FM Crepinsek, Z Curnel, Y Dahl, A Defila, C Donnelly, A Filella, Y Jatcza, K Mage, F Mestre, A Nordli, O Penuelas, J Pirinen, P Remisova, V Scheifinger, H Striz, M Susnik, A Van Vliet, AJH Wielgolaski, FE Zach, S Zust, A
GLOBAL CHANGE BIOLOGY 12:10 1969-1976
Global climate change impacts can already be tracked in many physical and biological systems; in particular, terrestrial ecosystems provide a consistent picture of observed changes. One of the preferred indicators is phenology, the science of natural recurring events, as their recorded dates provide a high-temporal resolution of ongoing changes. Thus, numerous analyses have demonstrated an earlier onset of spring events for mid and higher latitudes and a lengthening of the growing season. However, published single-site or single-species studies are particularly open to suspicion of being biased towards predominantly reporting climate change-induced impacts. No comprehensive study or meta-analysis has so far examined the possible lack of evidence for changes or shifts at sites where no temperature change is observed. We used an enormous systematic phenological network data set of more than 125 000 observational series of 542 plant and 19 animal species in 21 European countries (1971-2000). Our results showed that 78% of all leafing, flowering and fruiting records advanced (30% significantly) and only 3% were significantly delayed, whereas the signal of leaf colouring/fall is ambiguous. We conclude that previously published results of phenological changes were not biased by reporting or publication predisposition: the average advance of spring/summer was 2.5 days decade(-1) in Europe. Our analysis of 254 mean national time series undoubtedly demonstrates that species’ phenology is responsive to temperature of the preceding months (mean advance of spring/summer by 2.5 days degrees C-1, delay of leaf colouring and fall by 1.0 day degrees C-1). The pattern of observed change in spring efficiently matches measured national warming across 19 European countries (correlation coefficient r=-0.69, P < 0.001).